Conventional pattern generation systems for patterning large workpieces also create the pattern in stripes, swaths or rectangles. The boundaries between them, commonly referred to as butting or stitching boundaries create undesirable artifacts that may be visible in the final pattern. U.S. Pat. No. 5,495,279, the entire contents of which are incorporated herein by reference, illustrates a conventional method and apparatus for exposing substrates.
Extremely high throughput, for example in the range of about 0.05 m2/s through about 0.2 m2/s, combined with the large size of the workpieces, (e.g., in a range of about 5 m2 through 10 m2, and even 20 m2 or more), high optical resolution (e.g., in the range of about 3 microns through about 5 microns, and even down to 1 micron) and a sensitivity to “Mura” (visible striping or banding) defects creates a need to control certain errors to 50 nm or better. Conventional pattern generators, however, are unable to do so because merely scaling up conventional pattern generation techniques fails to achieve the required error control.
FIGS. 1D-1F illustrate example conventional pattern generators as disclosed in U.S. Pat. No. 6,542,178, U.S. Patent Publication No. 2004/0081499 and 2005/0104953, respectively, the entire contents of each of which are incorporated herein by reference.
FIG. 1D illustrates a drum plotter as disclosed in U.S. Pat. No. 6,542,178. As shown in FIG. 1D, the drum plotter includes a single writing unit writing optically on a rotating drum while moving along the axis of the drum. In the drum plotter of FIG. 1D, however, only the drum holding the workpiece, but not the single writing unit, is capable of rotating. Moreover, the drum plotter of FIG. 1D includes only a single exposure head, and each of the drum and the single writing unit are only capable of a single type of movement. That is, the drum is only capable of rotating, whereas the single writing unit is only capable of linear translational movement.
FIG. 1E illustrates an optical system as disclosed in U.S. Patent Publication No. 2004/0081499 for thermal transfer printing on glass substrates for LCD production. As shown in FIG. 1E, the optical system also includes a single optical writing unit moving along the axis of the rotating cylindrical workpiece holder. In the optical system of FIG. 1E, however, only the cylindrical workpiece, but not the single optical writing unit, is capable of rotating. Moreover, the optical system of FIG. 1E includes only a single exposure head, and each of the cylindrical workpiece and the single optical writing unit are only capable of a single type of movement. That is, the cylindrical workpiece is only capable of rotating, whereas the single optical writing unit is only capable of linear translational movement.
FIG. 1F illustrates a system writing optically on a rotating drum using multiple light sources coupled with fibers to a single writing unit and having the power of the light sources calibrated against a single detector as disclosed in U.S. Patent Publication No. 2005/0104953. As shown in FIG. 1F, the optical system also includes a single writing unit moving along the axis of the rotating drum. In the optical system of FIG. 1F, as in the optical systems of FIGS. 1D and 1E, only the cylindrical workpiece, but not the single optical writing unit, is capable of rotating. Moreover, the optical system of FIG. 1F includes only a single exposure head, and each of the cylindrical workpiece and the single optical writing unit are only capable of a single type of movement. That is, the cylindrical workpiece is only capable of rotating, whereas the single optical writing unit is only capable of linear translational movement.
The optical system of FIG. 1F further includes a photodetector for detecting the quantity of light emitted from the single optical writing unit. This photo detector, however, only detects quantity of light from the single optical writing unit.
Moreover, in each of FIGS. 1D-1F, the direction of rotation is parallel with one axis of the pattern and workpiece, while being perpendicular to the other axis of the pattern and workpiece.
FIG. 12A shows an example alignment of movements, produced by pattern generators such as those discussed above. Referring to FIG. 12A, three different coordinate systems are present. The first is the coordinate system of the pattern. In this example the patterns are display devices 1210, 1220, 1230 and 1240 formed on the workpiece glass. The second coordinate system is that of the writing mechanism 1260. In this example, the writing mechanism 1260 is an SLM. The third coordinate system is formed by the direction 1250 of movement of the writing mechanism 1260. In FIG. 12A, the three coordinate systems are aligned with each other. Arrow 1250 indicates the rotation direction of the workpiece relative to the pattern of the writing mechanism 1260. In the example shown in FIG. 12A, the rotation direction is parallel to a side of the writing mechanism (e.g., an SLM chip).
Conventional art direct write machines exposing liquid crystal display (LCD) workpieces using conventional pattern generators have write times of about twenty-four hours (one day). In these conventional pattern generators, writing width may be increased to reduce write time. However, this may require a larger number of optical channels and/or lenses, which may increase cost and/or complexity of the pattern generator. The speed at which the stage is moved may also be increased. However, controlling mechanical motion and/or vibration may be more difficult as stage speed increases. For example, an increase in speed and mass along with a decrease in application time may result in greater vibrations and/or resonances at higher frequencies in the mechanical structures. In addition, control and/or mechanical systems may not settle properly before writing a new stripe. Moreover, increased speed, vibration and/or a number of optical channels may increase cost and/or complexity of conventional pattern generators.